HISTORICALCLIMATOLOGY.COM

Article links climatic shifts to smallpox in the Great Plains. May 8, 2012.

In the latest issue of Environmental History environmental historian Adam Hodge argues that the climatic fluctuations of the Little Ice Age affected the productivity of the Great Plains grasslands, bison populations and, in turn, how migratory Native American tribes experienced smallpox. Between 1780 and 1782 smallpox killed more than half of natives living in the Great Plains, with mortality rates rising to 80% in the crowded villages of the Mandans, Hidatsas and Arikaras. While the historical spread of Old World diseases through densely packed, largely sedentary New World settlements should come as no surprise, high mortality rates among migratory tribes with low, scattered populations is more baffling. Trade and warfare had carried smallpox to the Great Plains by 1780, but Hodge argues that to understand why smallpox ravaged migratory tribes we need to understand their relationships with the environment of the Northern Plains.

Using scientific and documentary evidence, Hodge reconstructs how the climate of the Little Ice Age and the increased incidence of La Nina events influenced the extraordinary variability of seasonal precipitation and temperature across the Great Plains from the late 1770s to the early 1780s. According to Hodge, by stressing bison numbers, diminishing herd sizes and changing migration patterns the unreliable weather stimulated starvation among migratory native tribes. Starved individuals searched more widely for food, and increased interactions between native groups encouraged the spread of smallpox. Meanwhile, starvation compromises immune systems, rendering many among the migratory tribes more vulnerable to the disease. Climatic fluctuations did not cause the smallpox epidemic of 1780-1782, but they did affect why, according to historian Walter Prescott Webb, “the buffalo and the Plains Indians lived together, and together passed away.”